Currently, if a user setup Service Desk on an existing project, those issues reported by a particular user will not show in "My Request" in the user's portal. Even though the expected behavior is for those issues to show in "My Request" section, since they have reported those issue.
The same behavior happens when Service Desk is setup with a newly created project, and user import existing issues from another project.
The expected behavior is to have those issues reported by the user to show in the user's customer portal.
The workaround in the KB intend to convert existing issues to service desk requests: here